In rotating turbomachines, sealing elements of various types of construction are used for sealing different pressurized spaces. In the case of sealing between rotating and stationary machine components special sealing elements, which are movable in the radial direction and therefore can yield in the case of rotor vibrations or rotor deflections, are frequently used.
In this case, a distinction is essentially made between spring-type sealing segments, wherein springs press the sealing elements radially in the direction of the shaft, or so-called “retractable seals”. In this case, the springs are arranged between the segments so that a ring of sealing elements is pressed away from the shaft and only close as a result of the pressure drop across the place which is to be sealed during operation of the machine.
The technology with “retractable seals” is especially recommended for turbines in which during the starting and shutdown processes large relative movement between rotor and casing is to be expected. In this operating phase, the sealing elements are then sufficiently far away from the rotor, close at a specific pressure, and fulfill their function as sealing elements during operating conditions. In this case, the faultless and predictable function of the closing of the segments is important.
This function is especially hindered as a result of locking elements which are installed at the parting joint of the turbomachine and are necessary in order to secure at least the sealing segments which are arranged in the upper section of the casing of the turbomachine from falling out during installation.